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Journal of Nutrition Vol. 104 No. 6 June 1974, pp. 710-718
Copyright © 1974 by American Society for Nutrition
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Vitamin A Deficiency and the Glycoproteins of Rat Corneal Epithelium1

Yang-Cha Lee Kim2 and George Wolf

Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

The effect of vitamin A deficiency on in vitro incorporation of labeled precursors into glycoproteins of rat corneal epithelium was investigated. Whole corneas from deficient and pair-fed normal rats were incubated with radioactive precursors of glycoproteins; glycoproteins from the separated epithelial tissue were extracted and digested to yield glycopeptides. The glycopeptides eluted between 0.35 and 0.42 N LiCl by a continuous gradient from a DEAE—Sephadex column were found to be significantly affected by vitamin A deficiency. These affected glycopeptides were further separated by polyacrylamide gel electrophoresis and their carbohydrate content was assayed by gas—liquid chromatography. The results showed no fucose content and a much higher molar ratio of sialic acid to hexosamine (1.5 to 1.9) than that (0.3) of a similar vitamin A-sensitive glycopeptide previously isolated from rat small intestinal mucosa (De Luca, L., Schumacher, M. & Wolf, G. [1970] J. Biol. Chem. 245, 4551). It can be concluded that cornea contains a vitamin A-sensitive glycoprotein from which the affected glycopeptide is derived.

KEY WORDS: • vitamin A • cornea • corneal epithelium • glycoprotein • glucosamine

1 Publication no. 2258 from the Department of Nutrition and Food Science, M.I.T. Adapted from a thesis submitted by Yang Cha Lee Kim in partial fulfillment of the requirements for the Ph.D. degree, M.I.T., 1973. The authors gratefully acknowledge the Adelaide Breed Bayrd Foundation and NIH Grant EY515 for generous financial aid.

2 Present address: Department of Nutrition, Harvard School of Public Health, Boston, Mass. 02115.

Manuscript received 30 October 1973.




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